Dyeable bulky yarns based on polypropylene



United States Patent 3,137,989 DYEABLE BULKY YARNS BASED ON POLYPROPYLENE Aldo Fior and Emanuele Del Mauro, Terni, Italy, assignors to Montecatini Societa Generale per llndustria Mineraria e Chimica, Milan, Italy No Drawing. Filed Feb. 15, 1960, Ser. No. 8,513

Claims priority, application Italy Feb. 18, 1959 11 Claims. (Cl. 57-140) This invention relates to the preparation of dyeable bulky yarns based on polypropylene, particularly prevailingly isotactic polypropylene.

Yarns formed from continuous filaments of synthetic polymers are generally not adapted to used for purposes requiring a soft, light yarn having high covering power. When yarns meeting those needs are required, it is conventional to use a spun yarn, i.e., a yarn formed from short or stable fibres of the synthetic polymers, by the process normally used in making yarns from natural fibres such as cotton, wool, etc. For that reason, continuous filaments formed from synthetic polymers and synthetic resins generally have not been fabricated as such in practice but have been cut or otherwise disrupted to staplev fibres and the mass of short fibres thus obtained has then been converted into a spun yarn, as such or in a blend with natural fibres.

There is a great need in the art for a yarn formed from continuous synthetic polymer filaments but having the softness, light weight, and marked covering power of the yarns spun from staple fibres, and for a method of making such yarns, so that the operations involved in producing spun yarns, i.e., the crimping and cutting and the expensive after-treatments, can be eliminated.

Heretofore, no satisfactory process for making bulky, voluminous yarns from continuous filaments of the synthetic fibre-forming polymers has been available. In fact, some of the processes proposed for accomplishing that objective has been based on complex working cycles which are so expensive that the yarns obtained are neither entirely satisfactory nor competitive with spun yarns. Other less complex methods that have been suggested for producing continuous filament yarns of'increased bulk yield yarns the bulkiness of which is not permanent, or which have poor mechanical characteristics the values for which are substantially no better than, and practically the same as, the values for the mechanical properties of unstretched yarns.

In addition to the problem of a satisfactory process for making bulky, voluminous yarns, another more recent problem has been in the utilization of fibres from polypropylene. These fibres, though comparatively inexpensive, are inherently chemically inert, physically smooth and possessed of a hydrophobic surface. Because of these latter properties, great difiiculty has been observed in dyeing these fibres. Obviously not only the fibres are not amenable to dyeing, but so are their yarns.

Thus, it can be seen that this invention is concerned with the simultaneous solution of two problems.

One object of this invention is, therefore, to provide new dyeable yarns formed from continuous synthetic polypropylene filaments and having a bulk equal to, or higher than, that of staple yarns.

Another object is to provide dyeable bulky yarns of continuous synthetic polypropylene filaments which have a tenacity much higher than the tenacity normally possessed by staple synthetic fibres.

A further object is to provide a method for making dyeable light voluminous yarns of continuous filaments of polypropylene.

Other objects and advantages of this invention will beice come apparent on further study of the specification and appended claims.

These objects are obtained by the present invention in accordance with which polypropylene is mixed with various resins, more particularly with other polyolefins, epoxy resins, polyamides, polyalkylenimines, polyesters, polyaminotriazoles, polycaprolactam and mixtures thereof. This modified polypropylene mix is then spun into filaments.

The filamenetary products from the spinning operation are formed into a yarn, and the yarn is stretched under special conditions resulting in the introduction into the individual filaments of internal strains which are nonuniformly distributed along the filament length. The stretched yarn is then immersed abruptly into a hot medium in which it is heated rapidly to cause rapid shrinkage of the internally strained filaments. The rapid shrinkage of the irregularly strained filaments causes the formation of waves or crimps in the individual filaments resulting in a yarn which is crimped in a specific manner. The crimp is distributed irregularly along the filaments and yarn, with the loops disposed in different planes. The crimps serve to separate the individual filaments in the yarns from each other, so that air spaces are formed between the crimps. The air spaces contribute to the bulk, lightness, and insulating capacity of the yarn, and the crimps render the yarn highly elastic because they can stretch under tensile stress and then resume their initial shape as soon as the stress is removed. Moreover, the filaments and yarn obtained as described, are permanently crimped as shown by the tests illustrated hereinbelow.

The factors at the stretching stage which are determinative so far as obtaining our results is concerned are the rate at which the yarn is stretched, i.e. the rate at which the yarn is fed through the stretching zone, and the stretching temperature. For optimum results, the yarns are stretched at the maximum safe rate for the given temperature, the limit being the point at which the filaments break under the given conditions. In general, the yarns are subjected to a high rate of stretching at a relatively low temperature.

Stretching of the filaments results in orientation of the crystals in the direction of the filament axis. It is an important feature of the present method that the orientation of the crystals in the filaments is not destroyed by the processing producing the crimping, and that the final crimped yarn which is obtained has the high tensile strength which is a characteristic of oriented crystalline yarns.

This is in contrast to the results obtained by processes dependent on strong shrinking of the yarns, during which rnost of the orientation of the crystals is destroyed, and which yield a final yarn the tenacity of which is no better than the tenacity of the unstretched yarn.

In general, as is known, yarns of synthetic resins are stretched at a rate of 10 to 20 meters/minute and at a temperature between C. and 145 C.

Those conditions, which are conventional, do not result in the present bulky continuous filament yarns.

On the contrary, our dyeable, bulky, voluminous final yarns are obtained by feeding the yarn formed from the continuous filaments of the mix through the stretching zone at a rate of between 10 to 150 meters/minute, and at a temperature of between 20 C. and C.

The stretching ratio can vary from between 1:2 and 125.5. Release of the irregularly distributed internal strains introduced by the stretching, and the resulting scrimping of the yarn are effected at a temperature between about 50 C. and about 150 C. If desired, one can utilize further thermal treatment of dimensional stabilization under such conditions so as to prevent shrinking, at about 100 C. to C. for 5 to 30 minutes.

The specific conditions, and combination-of conditions, can be varied within the ranges stated, depending on the molecular weight of the polypropylene and the count of the yarn, both of which can influence the results obtained by the stretching. The ranges given, however, are generally operative for yarns having widely varying counts and for polypropylene of Widely different average molecular weight, so that regardless of the yarn count and molecular weight of the polymer, values in the ranges given for the stretching rate, stretching temperature, and relaxing temperature can be used in combination to produce the optimum results.

The passage of the yarns on one of more bodies with very sharp corners without causing a change in the direction of the yarns, said bodies being placed before or after, preferably after, the quick stretching roll and stretching hot plate, has also been found convenient.

The resins which are added to the polypropylene can be mixed in the proportion of about 1 to 20% of the total weight of the mix. It is to be noted that the dyeable bulky yarns obtained by the present invention can be dyed with a variety of dyes, including acid dyes, dispersed dyes and vat dyes.

In order to explain this invention with more lucidity, reference is made to the following non-limitative specific embodiments of the present invention.

Example 1 A mix consisting of 98% polypropylene and 2% epoxy resin obtained by condensation of epichlorohydrin with Bis-phenol-A, the trade name of Dow Chemical Co. for p-p-isopropylidenediphenol, is prepared. (All percentages in these examples refer to percentages by weight.)

The polypropylene presents the following character istics:

Intrinsic viscosity 1.48 Residue after heptane extraction percent 96.57 Ash content do 0.02

The mix is extruded under the following conditions:

Spinneret 20 holes, t 0.5 mm.

Head temperature 230 C.

Spinneret temperature 220 C.

Screw temperature 260 C.

Winding speed of the yarn 420 m./minute.

The yarn is then stretched under the following conditions:

Temperature C 22 Stretching ratio 1:2.8

1st-roll speed m./minute 39 Znd-roll speed do 110 The yarn is then subjected to shrinking in the presence of water vapor at 110 C. for minutes.

A bulky yarn having the following characteristics is thus obtained:

Tenacity g./den 1.16 Elongation "percent" 172.1 Relative bulk 1.70

The relative bulk is expressed as the ratio between the apparent volume of a yarn obtained according to this invention, wound up under a high tension on a reel, to the apparent volume of a continuous yarn obtained from the same mixture.

Example 2 A mix consisting of 98% polypropylene and 2% epoxy resin obtained by condensation of epichlorohydrin and Bis-phenol-A is prepared.

The polypropylene presents the following characteristics:

The yarn is subjected to shrinking in the presence of water vapor at 110 C. for 5 minutes.

A bulky yarn having the following characteristics is obtained:

Tenacity g./den 1.34 Elongation "percent" 17 8 Relative bull: 1.56

Example 3 With a polypropylene having the following characteristics:

Intrinsic viscosity 1.33 Residue after heptane extraction pcrcent 96.2 Ash content do..- 0.10

A mix consisting of 98% polypropylene and 2% epoxy resin obtained by condensation of epichlorohydrin and Bis-phenol-A is prepared.

This mix, after the addition of 0.1% stabilizer (4,4'- thio-bis-3-methyl-6-tert.butyl-phenol) and 0.2% TiO' as opacifier, is extruded under the following conditions:

Spinneret 20 holes, 41 0.5 mm. Head temperature 215 C.

Spinneret temperature 200 C.

Screw temperature 270 C.

Winding speed of the yarn 500 m./minute.

The yarn is then stretched under the following conditions:

Temperature C- 18 Stretching ratio 1:3 lst-roll speed m./minute 36 2nd-ro1l speed do 110 The yarn is finally subjected to shrinking in the presence of water vapor at 110 C. for 8 minutes.

A bulky yarn having the following characteristics is obtained:

Tenacity g./den 1.75 Elongation percent 70 Relative bulk 1.66

Example 4 With a polypropylene having the following characteristics:

Intrinsic viscosity 1.2 Residue after heptane extraction percent 89.8 Ash content do 0.04

A mix consisting of polypropylene, 2% polyethylemmine and 3% epoxy resin obtained from eipchlorohydrin and "Bis-phenol-A is prepared. The mix is extruded under the following conditions:

Spinneret 20 holes, 0.5 mm.

Head temperature 200 C. Spinneret temperature 190 C. Screw temperature 240 C. Winding speed of the yarn 500 m./minute.

The yarn is then stretched under the following conditions:

Temperature C 27 Stretching ratio 1:2.2 lst-roll speed m./minute 49 2nd-rol1 speed do 108 The yarn is finally subjected to shrinking in the presence of Water Vapor at 110 C. for 5 minutes.

A bulky yarn having the following characteristics is obtained:

Tenacity g. /den 1.4 Elongation percent 110.6 Relative bulk 1.19

Together with the polyalkylenimines, a dispersant such as cetyl or stearyl alcohol, stearic or terephthalic acid, benzoin, furoin, stearates, stearic acid amides, etc., can be used.

Example 5 With a polypropylene having the following characteristics:

Intrinsic viscosity 1.28 Residue after heptane extraction percent 94.2 Ash content do 0.02

A mix consisting of 95% polypropylene and 5% epoxy resin obtained from epichlorohydrin and Bis-phenol-A is prepared. The mix is extruded under the following conditions:

The yarn is subjected to shrinking in the presence of Water vapor at 105 C. for 10 minutes.

A bulky yarn having the following characteristics is obtained:

Tenacity g./den 1.47

Elongation percent 175 Relative bulk 1.85

Example 6 With a polypropylene having the following characteristics:

Intrinsic viscosity 1.225 Residue after heptane extraction percent 99.55 Ash content d 0.034

A mix consisting of 95% polypropylene, and epoxy resin obtained from epichlorohydrin and Bis-phenol-A is prepared. The mix is extruded under the following conditions:

Spinneret N. 40 holes, 11: 0.5 mm. Head temperature 220 C. Spinneret temperature 210 C. Screw temperature 260 C.

Winding speed of the yarn 470 m./minute.

6 The yarn is then stretched under the following conditions:

Temperature C 20 lst-roll speed m./minute 36 2nd-roll speed do 110 Stretching ratio 1:3

The yarn is then subjected to shrinking in the presence of Water vapor at 105 C. for 10 minutes.

A bulky yarn having the following characteristics is obtained:

Tenacity g./den 1.27

Elongation percent 114 Relative bulk 1.4

Example 7 With a polypropylene having the following characteristics:

Intrinsic viscosity 1.29 Residue after heptane extraction percent 84.8 Ash content do 0.10

A mix consisting of polypropylene and 5% epoxy resin obtained from epichlorohydrin and Bis-phenol-A is prepared. This mix is extruded under the following conditions:

Spinneret N. 40 holes, 4 0.5 mm. Head temperature 220 C.

Spinneret temperature 210 C.

Screw temperature 260 C.

Winding speed of the yarn 480 m./minute.

The yarn is then stretched under the following conditions:

Temperature C 24 Stretching ratio 1:3 lst-roll speed m./minute 36 2nd-roll speed do 110 The yarn is subjected to shrinking in the presence of Water vapor at 110 C. for 5 minutes.

A bulky yarn having the following characteristics is obtained:

Tenacity g./den 1.3

Elongation percent 83 Relative bulk 1.73

Example 8 With a polypropylene having the following characteristics:

Intrinsic viscosity 1.29 Residue after heptane extraction percent 91.3 Ash content do 0.072

A mix of 97% polypropylene and 3% polycaprolactam is prepared. This mix is extruded under the following conditions:

Spinneret N. 40 holes, t 0.5 mm. Head temperature 220 C.

Spinneret temperature 210 C.

Screw temperature 260 C.

Winding speed of the yarn 480 m./minute.

The yarn is then stretched under the following conditions:

Temperature C 20 Stretching ratio 1:3 lst-roll speed m./minute 35 2nd-roll speed do The yarn is subjected to shrinking in the presence of water vapor at C. for 5 minutes.

A bulky yarn having the following characteristics is obtained:

Tenacity g./den 1.76 Elongation percent 93 Relative bulk 1.19

All the exemplified bulky yarns result in attractively dyed materials.

With reference to the examples utilizing epoxy resins, it is considered that either aromatic or aliphatic epoxy resins are satisfactory.

With reference to the polyolefins that can be used in conjunction with polypropylene, such polymers as polyethylene and polystyrene are satisfactory.

Whereas this invention is suitable for crystalline polypropylene, it is particularly meritorious with the utilization of a polypropylene consisting prevailingly (over 50%) of isotactic macromolecules.

For a detailed description and process for making these prevailingly isotactic polypropylenes, which it is to be noted are regular head-to-tail, linear polymers, reference is made to the US. patent to Natta et al., 2,882,263, of April 14, 1959. For a publication, see the Journal of Polymer Science, April 1955, vol. XIV, Issue No. 82, pp. 143-154.

It is understood that the inventors intend to claim, as a part of their invention, any variation, substitution and changes that lie within the scope of the invention and the hereinafter appended claims and intend to include within the scope of said claims such changes as may be apparent to those skilled in the art in the practice of the principles of this invention and within the scope as set forth in the hereinabove-stated specification.

What is claimed is:

1. A process for producing a dyeable bulky continuous filament yarn which consists essentially of stretching a yarn formed from smooth continuous filaments of a mixture consisting essentially of crystalline polypropylene and from about 1 to 20%, based on the total weight of the mixture, of another resin selected from the group consisting of: polyolefins, epoxy resins, polyamides, polyalkylenimines, polyesters, polyaminotriazoles, polycaprolactam and mixtures thereof; at a temperature between 20 C. and 110 C. and at the highest rate of stretching which the filaments will withstand without breaking, by feeding the yarn through a stretching zone at the rate of 10 to 150 meters per minute to introduce irregularly distributed internal strains into the filaments, and then rapidly heating the stretched yarn at a temperature between 3 about C. and C., without applying tension to the yarn, to relax the irregularly distributed internal strains introduced by the stretching and obtain a yarn the synthetic polymer filaments of which are crimped irregularly along their length, with the loops disposed in different planes.

2. The process of claim 1, wherein the polypropylene consists prevailingly of isotactic macromolecules.

3. The process of claim 2, wherein the stretching ratio is about between 1:2 to 1:55.

4. The process of claim 1, wherein the resin mixed with the polypropylene is polyethylene.

5. The process of claim 1, wherein the resin mixed with the polypropylene is polystyrene.

6. The process of claim 1, wherein the resin mixed with the polypropylene is an aromatic epoxy resin resulting from the reaction of epichlorohydrin with p-p-isopropylidenediphenol.

7. The process of claim 1, wherein the resin mixed with the polypropylene is a polyamide.

8. The process of claim 1, wherein the resin mixed with the polypropylene is a polyalkylenimine.

9. The process of claim 1, wherein the resin mixed with the polypropylene is a polyester.

10. The process of claim 1, wherein the resin mixed with the polypropylene is a polyaminotriazole.

11. The process of claim 1, characterized by the additional step of dyeing the bulky yarns with a dye selected from the group consisting of: acid dyes, dispersed acetate dyes and vat dyes.

References Cited in the file of this patent UNITED STATES PATENTS 2,369,395 Heymann Feb. 13, 1945 2,527,863 Webb Oct. 31, 1950 2,602,964 Sisson July 15, 1952 2,604,689 Hebeler July 29, 1952 2,669,001 Keen Feb. 16, 1954 2,727,024 Field et al. Dec. 13, 1955 2,783,609 Breen Mar. 5, 1957 2,869,967 Breen Jan. 20, 1959 2,917,805 Rokosz Dec. 22, 1959 2,927,904 Cooper Mar, 8, 1960 2,950,267 Thompson et al Aug. 23, 1960 2,956,042 Underwood et a1 Oct. 11, 1960 FOREIGN PATENTS 760,179 Great Britain Oct. 31, 1956 

1. A PROCESS FOR PRODUCING A DYEABLE BULKY CONTINUOUS FILAMENT YARN WHICH CONSISTS ESSENTIALLY OF STRETCHING A YARN FORMED FROM SMOOTH CONTINUOUS FILAMENTS OF A MIXTURE CONSISTING ESSENTIALLY OF CRYSTALLINE POLYPROPYLENE AND FROM ABOUT 1 TO 20%, BASED ON THE TOTAL WEIGHT OF THE MIXTURE, OF ANOTHER RESIN SELECTED FROM THE GROUP CONSISTING OF: POLYOLEFINS, EPOXY RESINS, POLYAMIDES, POLYALKYLENIMINES, POLYESTERS, POLYAMINOTRIAZOLES, POLYCAPROLACTAM AND MIXTURES THEREOF; AT A TEMPERATURE BETWEEN 20* C. AND 110* C. AND AT THE HIGHEST RATE OF STRETCHING WHICH THE FILAMENTS WILL WITHSTAND WITHOUT BREAKING, BY FEEDING THE YARN THROUGH A STRETCHING ZONE AT THE RATE OF 10 TO 150 METERS PER MINUTE TO INTRODUCE IRREGULARLY DISTRIBUTED INTERNAL STRAINS INTO THE FILAMENTS, AND THEN RAPIDLY HEATING THE STRETCHED YARN AT A TEMPERATURE BETWEEN ABOUT 50* C. AND 150* C., WITHOUT APPLYING TENSION TO THE YARN, TO RELAX THE IRREGULARLY DISTRIBUTED INTERNAL STRAINS INTRODUCED BY THE STRETCHING AND OBTAIN A YARN THE SYNTHETIC POLYMER FILAMENTS OF WHICH ARE CRIMPED IRREGULARLY ALONG THEIR LENGTH, WITH THE LOOPS DISPOSED IN DIFFERENT PLANES. 